The present invention relates to heat-resistant crimped yarn comprising heat-resistant high-functional fibers such as aramid fibers, and to a method for producing it. More precisely, the invention relates to heat-resistant crimped yarn which has not only excellent heat resistance, flame retardancy and high tenacity characteristics, but also a good elongation percentage in stretch, a good stretch modulus of elasticity and a good appearance, and which fluffs little and releases little dust; and relates to a method for producing the heat-resistant crimped yarn characterized by treatment with high-temperature high-pressure steam or high-temperature high-pressure water or by dry heat treatment.
The invention also relates to a bulky and stretchable fibrous product of the heat-resistant crimped yarn. In particular, it relates to working clothes and gloves necessary for protecting workers"" bodies and hands in various workplaces, for example, those for steel workers working around high-temperature blast furnaces, those for sheet metal welders, those for farmers, those for painters in the field of automobiles or electric and electronic appliances, those for workers in the field of precision machines, airplanes or information systems, those for sportsmen, those for surgeons, etc.
General thermoplastic synthetic fibers such as nylon or polyester fibers melt at about 250xc2x0 C. or so. However, heat-resistant high-functional fibers such as aramid fibers, holaromatic polyester fibers and polyparaphenylene-benzobisoxazole fibers do not melt at about 250xc2x0 C. or so, and their decomposition temperature is about 500xc2x0 C. or so and is high. The critical oxygen index of the non-heat-resistant general fibers, nylon or polyester fibers is about 20 or so, and the fibers well burn in air. However, the critical oxygen index of the heat-resistant high-functional fibers such as those mentioned above is at least about 25, and the fibers may burn in air when they are brought near to a heat source of flames, but could not continue to burn if they are moved away from the flames. To that effect, the heat-resistant high-functional fibers have excellent heat resistance and flame retardancy. Therefore, aramid fibers, a type of heat-resistant high-functional fibers are favorable to clothes for use in high risk of exposure to flames and high temperatures, for example, for fireman""s clothes, racer""s clothes, steelworker""s clothes, welder""s clothes, etc. Above all, para-aramid fibers having the advantages of heat resistance and high tenacity are much used for sportsman""s clothes, working clothes, ropes, tire cords and others that are required to have high tear strength and heat resistance. In addition, as they are hardly cut with edged tools, the fibers are also used for working gloves. On the other hand, meta-aramid fibers are resistant to heat and have good weather resistance and chemical resistance, and they are used for fireman""s clothes, heat-insulating filters, heat-resistant dust-collecting filters, electric insulators, etc.
Heretofore, when the heat-resistant high-functional fibers are formed into fibrous products such as clothes, they are used merely in the form of non-crimped filaments or spun yarn. However, even when such non-crimped yarn of filaments or spun yarn is worked into fabrics and formed into clothes such as fireman""s clothes, racer""s clothes and working clothes, the resulting clothes are poorly elastic as the yarn itself is not elastic. As a result, when the clothes are worn, they are problematic in that their feel is not good and they are unsuitable to exercises and working activities.
In particular, working gloves made of conventional non-crimped yarn are unsuitable to use in the industrial fields of airplanes, information systems and precision machines in which precision parts are handled, as they do not well fit with worker""s hands. Using the gloves in those industrial fields often results in the reduction in the working efficiency. In the field of medicine, for example, in the field of surgical operations of treating AIDS cases and the like that will cause infection by blood, the surgeons wear rubber gloves or elastomer gloves (hereinafter referred to as rubber gloves) to protect themselves from the patient""s blood. Ambulance men take care of unspecified, wounded or sick persons, and they wear rubber gloves to protect themselves from the blood and body fluid of patients who are not yet identified as infectious. However, rubber gloves will be readily broken by operation tools such as surgical knives, and they could not completely protect the medical and surgical workers such as physicians, surgeons and ambulance men, from surgical knives, syringe needles and others stained with patient""s blood. In that situation, it may be taken into consideration to wear woven or knitted gloves of heat-resistant high-functional fibers with high mechanical strength such as those mentioned above, inside rubber gloves. However, as mentioned hereinabove, the conventional gloves of heat-resistant high-functional fibers are poorly elastic and therefore lower the working efficiency of the medical and surgical workers such as physicians, surgeons and ambulance men. Accordingly, thin, elastic and tough gloves capable of being worn inside rubber gloves without detracting from the working efficiency are desired.
Heretofore, however, spun yarn is produced by spinning short fibers generally having a length of around 38 mm or around 51 mm or so, and the edges of the short fibers often protrude out of the surface of the spun yarn to form fluffs therearound. Working clothes and gloves made of spun yarn of heat-resistant high-functional fibers release the fluffs, when rubbed while they are used. Therefore, using them in clean rooms with no dust in air therein, or in painting factories in which dust, when adhered to the surfaces of painted products, detracts from the commercial value of the products is problematic. In that situation, working clothes, gloves and other fibrous products of heat-resistant high-functional fibers, which fluff little and release little dust are desired.
As described hereinabove, fibrous products of non-crimped yarn of heat-resistant high-functional fibers are unsuitable to exercises and working activities, and they fluff and release dust. In order to solve the problems, it is desired to provide heat-resistant crimped which has a good elongation percentage in stretch, a good stretch modulus of elasticity and a good appearance, not losing the excellent characteristics of good heat resistance and flame retardancy intrinsic to heat-resistant high-functional fibers, and which fluffs little and releases little dust.
To meet the requirements now in the market, various studies and proposals have been made, relating to heat-resistant crimped yarn and to a method for crimping heat-resistant high-functional fibers (Japanese Patent Laid-Open Nos. 19818/1973, 114923/1978, 27117/1991). Concretely, one proposal is to apply a method for crimping ordinary thermoplastic synthetic fibers such as nylon or polyester fibers. For example, known is a method of forcedly crimping high-elasticity fibers such as para-aramid fibers mixed with low-elasticity fibers (Japanese Patent Laid-Open No. 192839/1989). Also known is crimped yarn produced by a false-twisting method in which aramid fibers are false-twisted and crimped by the use of a non-contact heater heated at a temperature not lower than that at which the fibers begin to decompose but lower than the decomposition point of the fibers (for meta-aramid fibers, the temperature is 390xc2x0 C. or higher but lower than 460xc2x0 C.), and thereafter subjected to thermal relaxation (Japanese Patent Laid-Open No. 280120/1994).
However, the known methods could not still solve all the outstanding technical problems which are how to produce high-quality crimped yarn having a good elongation percentage in stretch and a good stretch modulus of elasticity; how to prevent yarn quality deterioration, for example, tenacity reduction and color change under heat of yarn produced, and how to prevent the yarn from fluffing and from being cut or broken; and how to realize easy process control, simplification of production lines, increased productivity, and cost reduction. At present, therefore, no one has succeeded in industrial production of heat-resistant crimped yarn having a good elongation percentage in stretch and so on, not losing the physical properties intrinsic to the constituent fibers.
In view of the problems in the related art noted above, one object of the present invention is to provide heat-resistant crimped yarn which comprises heat-resistant high-functional fibers and has a good elongation percentage in stretch, a good stretch modulus of elasticity and a good appearance, for which the quality deterioration of the constituent heat-resistant high-functional fibers through heat treatment in the production process is reduced as much as possible, and which therefore does not lose the excellent properties of good heat resistance and flame retardancy intrinsic to the heat-resistant high-functional fibers, and which fluffs little and releases little dust.
Another object of the invention is to provide a method for producing the heat-resistant crimped yarn practicable in point of the productivity, the necessary equipment and the production costs.
Still another object of the invention is to provide fibrous products, especially gloves of which the advantages are that (a) they are elastic and resistant to heat, and they have good mechanical strength and a good appearance, (b) they well fit wearer""s bodies including hands and are suitable to exercises and working activities, (c) they fluff little and release little dust, and (d) they are easy to produce on an industrial scale as the process control is easy, the productivity is high and the production costs is low.
We, the present inventors have assiduously studied so as to attain the objects as above, and, as a result, have found that, when heat-resistant high-functional fibers are used in the form of crimped yarn having a specific elongation percentage in stretch, a specific stretch modulus of elasticity and a specific tenacity and not deteriorating under heat, in producing fibrous products, then the suitability of the resulting fibrous products to exercises and working activities is significantly improved, as compared with those used in the form of non-crimped yarn such as filaments or spun yarn, and that the fibrous products fluff little and release little dust even when rubbed while they are used. The fibrous products, which we have produced in the manner as above, solve all the outstanding problems in the prior art mentioned hereinabove.
We have further studied the method for producing the heat-resistant crimped yarn, and, as a result, have found that, when heat-resistant high-functional fiber filaments are first twisted in a primary twisting step, then heat-set for twist fixation through treatment with high-temperature high-pressure steam or high-temperature high-pressure water or through dry heat treatment, and finally untwisted by again twisting them in the direction opposite to the primary twisting direction, then the above-mentioned heat-resistant crimped yarn of high quality can be produced.
Heat-resistant high-functional fiber filaments are slippery. Therefore weaving or knitting them into gloves by the use of weaving or knitting machines is often difficult. In this connection, we have found that the heat-resistant crimped yarn of the invention solves the problem. We have further found that bulky and stretchable fibrous products such as gloves made of the heat-resistant crimped yarn of the invention have an advantage in that they fluff little and release little fluff. As so mentioned hereinabove, spun yarn of short fibers fluffs since the edges of the constituent short fibers protrude out of the surface of the yarn, and therefore, fibrous products made of spun yarn of heat-resistant high-functional fibers release fluffs when rubbed while they are used. As opposed to such spun yarn, the heat-resistant crimped yarn of the invention is composed of long fibers and therefore has no fluffs on its surface. Not having edges of short fibers therearound, therefore, fibrous products such as working clothes made of the heat-resistant crimped yarn of the invention fluff little and therefore do not release fluffs even when rubbed while they are used.
In the industrial fields of precision machines, airplanes and information systems, for example, in the working site for fabricating electronic parts for airplanes, computers and the like, the working space must be kept all the time clean. If the working gloves used in the site are deteriorated, they will soon release fibrous dust in the working space, in which, however, the trouble is unacceptable. Accordingly, the fibrous products especially the gloves of the invention are especially useful in these industrial fields, as having the advantage of fluffing little and releasing little dust. In painting factories in which construction materials of aluminum, electric and electronic appliances for household use, or automobile parts are painted, fibrous fluffs and dust, if they have been adhered to the surfaces of the painted products, detract from the commercial value of the products. In these, therefore, the fibrous products especially the gloves of the invention are also useful, since they fluff little and release little dust.
Having further studied, we, the present inventors have completed the present invention.
Specifically, the invention relates to the following:
(1) Heat-resistant crimped yarn not deteriorating under heat, which comprises heat-resistant high-functional fibers having a mono-filament fineness of from 0.02 to 1 tex, and of which the elongation percentage in stretch is at least 6%, the stretch modulus of elasticity is at least 40%, and the tenacity falls between 0.15 and 3.5 N/tex;
(2) The heat-resistant crimped yarn of above (1), wherein the heat-resistant high-functional fibers are para-aramid fibers, holaromatic polyester fibers or polyparaphenylene-benzobisoxazole fibers, and of which the tenacity falls between 0.5 and 3.5 N/tex;
(3) The heat-resistant crimped yarn of above (2), for which the para-aramid fibers are polyparaphenylene-terephthalamide fibers;
(4) The heat-resistant crimped yarn of above (1), wherein the heat-resistant high-functional fibers are meta-aramid fibers, and of which the elongation percentage in stretch falls between 50 and 300%;
(5) The heat-resistant crimped yarn of above (4), wherein the meta-aramid fibers are polymetaphenylene-isophthalamide fibers;
(6) A bulky and stretchable fibrous product of the heat-resistant crimped yarn of any of above (1) to (5), wherein the amount of the heat-resistant crimped yarn is for at least 50% of the fibrous part of the product;
(7) The bulky and stretchable fibrous product of above (6), which is for gloves;
(8) The gloves of above (7) for use in the industrial fields of precision machines, airplanes, information systems, automobiles, electric and electronic appliances, and in the field of surgical operations and sanitary facilities;
(9) The bulky and stretchable fibrous product of above (6), which is for fireman""s clothes, racer""s clothes, steel worker""s clothes, welder""s clothes or painter""s clothes;
(10) A method for producing heat-resistant crimped yarn, which comprises twisting heat-resistant high-functional fiber filaments, heat-setting them through treatment with high-temperature high-pressure steam or high-temperature high-pressure water, and thereafter untwisting them;
(11) The method for producing heat-resistant crimped yarn of above (10), wherein the heat-resistant high-functional fiber filaments are twisted to a twist parameter, K represented by the following formula, of from 5,000 to 11,000, and are heat-set through treatment with high-temperature high-pressure steam or high-temperature high-pressure water at a temperature falling between 130 and 250xc2x0 C.:
K=txc3x97D1/2
wherein t indicates the count of twists (/m) of the filaments; and D indicates the fineness (tex) thereof;
(12) The method for producing heat-resistant crimped yarn of above (10) or (11), wherein the heat-resistant high-functional fibers are selected from the group consisting of para-aramid fibers, meta-aramid fibers, holaromatic polyester fibers and polyparaphenylene-benzobisoxazole fibers;
(13) The method for producing heat-resistant crimped yarn of above (12), wherein the para-aramid fibers are polyparaphenylene-terephthalamide fibers;
(14) The method for producing heat-resistant crimped yarn of any of above (10) to (13), wherein the heat-resistant crimped yarn produced has an elongation percentage in stretch of at least 6% and a stretch modulus of elasticity of at least 40%;
(15) A bulky and stretchable fibrous product made of the heat-resistant crimped yarn obtained in the production method of above (12);
(16) A method for producing heat-resistant crimped yarn, which comprises twisting heat-resistant high-functional fiber filaments, heat-setting them through dry heat treatment at a temperature not higher than the decomposition point of the heat-resistant high-functional fibers, and thereafter untwisting them;
(17) The method for producing heat-resistant crimped yarn of above (16), wherein the heat-resistant high-functional fiber filaments are twisted to a twist parameter, K represented by the following formula, of from 5,000 to 11,000, then heat-set through dry heat treatment at a temperature falling between 140 and 390xc2x0 C., and thereafter untwisted:
K=txc3x97D1/2
wherein t indicates the count of twists (/m) of the filaments; and D indicates the fineness (tex) thereof;
(18) The method for producing heat-resistant crimped yarn of above (16) or (17), wherein the process of twisting the heat-resistant high-functional fiber filaments, heat-setting them through dry heat treatment and thereafter untwisting them is effected continuously;
(19) The method for producing heat-resistant crimped yarn of any of above (16) to (18), wherein the dry heat treatment is effected at a temperature falling between 200 and 300xc2x0 C.;
(20) The method for producing heat-resistant crimped yarn of any one of above (16) to (19), wherein the heat-resistant high-functional fibers are selected from the group consisting of para-aramid fibers, meta-aramid fibers, holaromatic polyester fibers and polyparaphenylene-benzobisoxazole fibers;
(21) The method for producing heat-resistant crimped yarn of any one of above (16) to (20), wherein the para-aramid fibers are polyparaphenylene-terephthalamide fibers;
(22) The method for producing heat-resistant crimped yarn of any one of above (16) to (21), wherein the heat-resistant crimped yarn produced has an elongation percentage in stretch of at least 6% and a stretch modulus of elasticity of at least 40%;
(23) A bulky and stretchable fibrous product made of the heat-resistant crimped yarn obtained in the method of any one of above (16) to (22);
(24) A method for producing heat-resistant crimped yarn, which comprises knitting heat-resistant high-functional fiber filaments into a knitted fabric, then heat-setting the knitted fabric through dry heat treatment or through treatment with high-temperature high-pressure steam or high-temperature high-pressure water, and thereafter unknitting it;
(25) The method for producing heat-resistant crimped yarn of above (24), wherein the knitted fabric of heat-resistant high-functional fiber filaments is heat-set through treatment with high-temperature high-pressure steam or high-temperature high-pressure water at a temperature falling between 130 and 250xc2x0 C. for a period of time falling between 2 and 100 minutes, and then this is unknitted;
(26) The method for producing heat-resistant crimped yarn of above (24), wherein the knitted fabric of heat-resistant high-functional fiber filaments is heat-set through with dry heat treatment at a temperature falling between 140 and 390xc2x0 C., and then this is unknitted;
(27) The method for producing heat-resistant crimped yarn of above (25) or (26), wherein the heat-resistant crimped yarn produced has the elongation percentage in stretch of at least 6.5%;
(28) Gloves made by weaving or knitting yarn that contains crimped yarn of heat-resistant high-functional fibers;
(29) Gloves of above (28), wherein the crimped yarn has an elongation percentage in stretch of from 6% to 30% and a stretch modulus of elasticity of from 40 to 100%;
(30) Gloves of above (28) or (29), wherein the heat-resistant high-functional fibers are selected from the group consisting of para-aramid fibers, meta-aramid fibers, holaromatic polyester fibers and polyparaphenylene-benzobisoxazole fibers;
(31) Gloves of above (30), wherein the para-aramid fibers are polyparaphenylene-terephthalamide fibers;
(32) Gloves of any of above (28) to (31), wherein the crimped yarn of heat-resistant high-functional fibers is produced by twisting heat-resistant high-functional fiber filaments, heat-setting them through dry heat treatment or through treatment with high-temperature high-pressure steam or high-temperature high-pressure water, and thereafter untwisting them; and
(33) Gloves of any of above (28) to (32), which are for use in the industrial fields of precision machines, airplanes, information systems, or in the field of surgical operations and sanitary facilities.